"I want to take this opportunity to once again thank the staff of Salisbury District Hospital for delivering such high quality care to these patients over the last few weeks," said Dr Christine Blanshard, Medical Director for Salisbury District Hospital.

"I am very proud both of our front-line staff and all those who support them."

BBC correspondent Duncan Kennedy says a corner appears to have been turned for Yulia Skripal, who is now in a stable condition.

However there is no news on what the long-term damage might be, he adds.

Meanwhile the police have placed cordons round a children's play area at Montgomery Gardens near Mr Skripal's home.

"Officers will be searching it as a precautionary measure," said Deputy Assistant Commissioner Dean Haydon.

The Skripals were admitted to hospital on 4 March after being found collapsed on a bench at the Maltings shopping centre in Salisbury.